The present invention relates to stackable drawn pieces as well as to a process and to an arrangement for manufacturing these pieces. In particular, the present invention relates to stackable drawn pieces made of sheet metal, having spacer knobs which are integrated in the drawn piece and are drawn in a bead-type manner and which rise from the wall of the drawn piece, which is situated transversely to the stacking direction. Thereby, the walls of the drawn piece situated transversely to the stacking direction have such a mutual distance that the walls, which are situated at an acute angle with respect to the stacking direction of the drawn pieces, come at most in a loose mutual contact and reliably engage in one another in a no-lock manner, the spacer knobs being arranged on the drawn pieces in the same position.
The present invention further relates to a process for manufacturing stackable drawn sheet-metal pieces, comprising the steps of deep-drawing blanks to a trough-shaped form, and drawing in the drawn blank bead-type spacer knobs which rise from a wall of the finished deformed at least one drawn piece, which is situated transversely to a stacking direction, such that walls of the at least one drawn piece extending transversely with respect the stacking direction are spaced and walls situated at an acute angle with respect to the stacking direction have, at most, a loose mutual contact and reliably engage in one another in a no-lock manner, the spacer knobs being situated above one another in a stack in the same position. An apparatus for manufacturing stackable drawn sheet-metal pieces comprises a drawing punch and a die for shaping the drawn pieces, a plurality of knob drawing punches and knob dies integrated therein for the molding-on of spacer knobs, the mutually facing front sides of each of the knob drawing punch and of the knob die being arranged in corresponding positions and constructed in a negative-mold-type fashion with respect to one another.
Drawn pieces as well as a process and an arrangement for manufacturing them are described in DE 43 12 287 C1. In order to prevent a locking of the drawn pieces, a rotary punch is provided for forming spacer knobs with an assigned rotary drive which, starting from a first drawn piece to be provided with spacer knobs, has a different rotating position at least in the case of the drawn piece to be deformed next. By way of the different alignment of the bead-type spacer knobs at mutually next or next but one adjacent drawn pieces, a locking of the drawn pieces in the stack is prevented.
The manufacturing and the control of the rotary punch requires, however, relatively high expenditures. Also, in a test inspection of several successive drawn pieces, the stacking must be interrupted because it is not certain whether the drawn piece to be stacked next has spacer knobs which are constructed such that this drawn piece will not lock in the up to now uppermost drawn piece.
It is an object of the present invention to provide an improved drawn piece and the apparatus and process for manufacturing the drawn piece so that a stacking without any locking of the drawn pieces can be more simply accomplished.
According to the present invention, this object has been achieved by providing that the spacer knobs are disposed above one another in the stack, and have the same dimensioning and alignment, and a diameter of a respective knob opening, on at least one partial circumferential area, is smaller than a diameter of the spacer knobs in an area of a free knob end. In addition, an area of a free end of the spacer knobs disposed above one another in the stack and, with respect to their dimensions and alignment, have the same construction is internally expanded with respect to a knob opening.
According to an improved arrangement, each knob drawing punch and each knob dies for the molding-on of the spacer knobs are non-rotatably arranged and at least each knob drawing punch is axially movably guided, and a deforming device for radial expansion of a knob base with respect to a knob opening, each knob die being provided with a recess for forming out of the spacer knob which is undercut.
As the result of the advantageous features of the present invention, a rotary drive for the rotary punch producing the spacer knobs as well as its rotary bearing are eliminated. For this purpose, the spacer knobs have identical shapes for all drawn pieces, with the same dimensions and the same alignment Then devices are used which deform the identically constructed spacer knobs such that, by way of the different diameters of the knob opening and the knob base or the free end of the spacer knobs, a locking of the deformed drawn pieces during stacking is prevented.
The uniform construction of the mutually non-lockable drawn pieces allows removal of several drawn pieces successively from the manufacturing operation for testing without the necessity of interrupting the further stacking operation. For drawn pieces with a high degree of deformation difficulty, such as inside door panels, the deformation of the spacer knobs takes place particularly efficiently because these drawn pieces must be drawn in several operating steps (steps, or strokes) and thus a deformation is possible which is parallel to these operating steps. The spacer knobs can be drawn in a separate drawing operation during the first deforming steps of the drawn piece or simultaneously with a deforming step which concerns the shaping of the drawn piece.